This supplementary material provides an overview of reactive oxygen species (ROS) signaling in plant stress responses. The review highlights the multiple pathways involved in ROS production and scavenging in plants, which determine the localization, duration, and intensity of ROS signals under normal conditions or during environmental stresses. ROS production occurs in various cellular compartments, including chloroplasts, peroxisomes, mitochondria, and the apoplast. ROS scavenging pathways are also present in these compartments and help to remove ROS produced during normal metabolism or under stress. The evolution of ROS metabolism in cells is discussed, emphasizing the role of ROS in the development of aerobic life and the integration of ROS-related pathways into the genomes of all aerobic organisms. The review also highlights the importance of ROS in plant signaling and stress responses, and the role of various enzymes and proteins in regulating ROS levels in plant cells. The supplementary tables provide additional information on the biochemical, physical, and molecular properties of different ROS and reactive nitrogen species (RNS) in cells, as well as the plant proteins and small molecules that regulate ROS levels. The review is supported by a range of references that provide further insight into the role of ROS in plant biology.This supplementary material provides an overview of reactive oxygen species (ROS) signaling in plant stress responses. The review highlights the multiple pathways involved in ROS production and scavenging in plants, which determine the localization, duration, and intensity of ROS signals under normal conditions or during environmental stresses. ROS production occurs in various cellular compartments, including chloroplasts, peroxisomes, mitochondria, and the apoplast. ROS scavenging pathways are also present in these compartments and help to remove ROS produced during normal metabolism or under stress. The evolution of ROS metabolism in cells is discussed, emphasizing the role of ROS in the development of aerobic life and the integration of ROS-related pathways into the genomes of all aerobic organisms. The review also highlights the importance of ROS in plant signaling and stress responses, and the role of various enzymes and proteins in regulating ROS levels in plant cells. The supplementary tables provide additional information on the biochemical, physical, and molecular properties of different ROS and reactive nitrogen species (RNS) in cells, as well as the plant proteins and small molecules that regulate ROS levels. The review is supported by a range of references that provide further insight into the role of ROS in plant biology.